This disclosure relates generally to the protection of electrical and electronic circuits from short circuit conditions. More particularly, but not by way of limitation, this disclosure relates to a technique for protecting parallel coupled battery cells from short circuit and over-temperature conditions.
A thermal cutoff (TCO) is a device that interrupts electric current within a circuit when the TCO is heated to a predetermined threshold. TCOs may be composed of material that melts, or bimetallic strips that separate when heated to a predetermined threshold and function on the order of seconds. TCOs may be characterized as a two-terminal circuit element. During normal operation a TCO allows current flow between its two terminals and, when the current exceeds the TCO's threshold, it passes no current. When conducting, a typical TCO can present 10 milli-ohms (mΩ)±5 mΩ resistance to the current flow.